The new study underlines that when a pregnant woman breathes polluted air, the invisible particulate matter is able to reach the placenta through the blood stream.

New Delhi: Particulate matter inhaled by pregnant women may make it through the placenta and reach the foetus, new evidence shows for the first time. According to scientists, this makes the made the links between exposure to air pollution and issues such as premature birth, low birth weight, infant mortality and childhood respiratory problems clearer.

While studies have long linked air pollution with the poor development of the foetus, the new study underlines that when a pregnant woman breathes polluted air, the invisible particulate matter is able to reach the placenta through the blood stream. This study was done by Dr Norrice Liu, a paediatrician and clinical research fellow, and Dr Lisa Miyashita, a post-doctoral researcher. Both are members of Professor Jonathan Grigg's research group at Queen Mary University of London, UK.

In a statement, Miyashita said, "We were interested to see if these effects could be due to pollution particles moving from the mother's lungs to the placenta. Until now, there has been very little evidence that inhaled particles get into the blood from the lung."

Although India has made significant improvement in terms of childhood mortality, it still accounts for the world's highest number of deaths among children below the age of five and in newborns. Add to this, the incontestable fact that India tops the world in bad air quality — the WHO points out that of the 20 most polluted cities in the world, 14 are in India.

For the study, researchers worked with five pregnant women, all non-smokers, living in London, due to have planned caesarean section deliveries at the Royal London Hospital. Each gave birth to a healthy baby without complications and provided permission to researchers to study their placentas after delivery. The research focused on placental macrophages — cells that are a part of the immune system that engulf harmful material such as bacteria or particulate matter. In the placenta, they protect the foetus.

A study of 3,500 placental macrophage cells from the five placentas led to the discovery of 60 cells that between them contained 72 small black areas that researchers believe were carbon particles. On an average, each placenta contained around five square micrometres of this black substance. A detailed study of placental macrophages from two placentas through an electron microscope confirmed the findings.

"We do not know whether the particles we found could also move across into the foetus, but our evidence suggests that this is indeed possible. We also know that the particles do not need to get into the baby's body to have an adverse effect, because if they have an effect on the placenta, this will have a direct impact on the foetus," Liu said.